Fabrics used for underpadding for limb casts have included cotton, foams, synthetics such as polyester fiberfill and wool. The major functions of underpadding are cushioning. Most currently available underpaddings lose some of their functionality when immersed in water. Water can cause padding to compress or to shift due to weight gain. In addition, a water-saturated underpadding is not useful for transfer of moisture away from the skin. This loss of function is especially critical when the padding is worn by a person for extended periods. Prolonged wetness next to the skin causes skin breakdown and possible infection sites. It is therefore desirable to provide a padding which will not be adversely affected by exposure to water. It is also desirable to provide padding that will allow the transfer of water vapors so that perspiration and other body fluids can escape.
In the past, several methods have been used to overcome some of the drawbacks of padding. Quilting has been used to prevent padding from shifting, while maintaining high loft and bulkiness desirable in padding. Bonding padding to a fabric backing also prevents shifting. Fiberfill consists of crimped fibers to help maintain fluffiness and air space, even upon exposure to water. Hollow fibers also contain air space which add insulating value. Synthetic fibers are generally less absorbent than natural ones and have been used to wick fluids away from the skin into more absorbent backings. However, fluid saturation results in loss of function.
Large quantities of padding are used under immobilizing orthopedic casts or braces. Traditional cast underpadding consists of cotton or polyester wraps in 2 inch to 6 inch widths. Care is taken when applying the underpadding to avoid folds or creases which can cause pressure sores to the skin. The immobilizing material applied on top of this padding is usually made of plaster of Paris or polyurethane-coated fiberglass. Plaster of Paris immobilizing materials disintegrate when in contact with water and cast wearers are told not to expose the cast to any water at all. Cast wearers with fiberglass immobilizing material are usually told not to immerse the cast in water, even though polyurethane casts can withstand water immersion. If a traditionally padded polyurethane cast is immersed, the padding remains wet for many hours, and the result can be skin maceration. In some cases, this maceration can lead to skin breakdown and infection by bacteria or fungi. Cast padding material manufacturers often caution against water immersion and state that if a cast is wet, it should be completely dried with a hair dryer. This drying process can take several hours and patient compliance is extremely low. Some cast wearers use plastic bags with rubber bands around the end to keep water away from the cast while showering. Water often enters the bag and wets the padding which causes discomfort to the wearer. As a result, many cast wearers do not want to get their cast wet and spend the time they are wearing a cast without a normal shower or bath. In addition, cast wearers cannot swim or use any form of hydrotherapy.
It is widely recognized that paddings must be "breathable" to be comfortable. However, it is not necessary that air pass through the padding for it to be comfortable, only that water vapor from perspiration or other sources be transmitted from the skin outwards through the padding. "Breathability" and the ability to transport interior moisture vapor to the external environment are used interchangeably herein.
U.S. Pat. No. 5,102,711 relates to a flexible, breathable, nonlinting composite comprising a middle layer of padding and a top and bottom comprising a sheet of porous water impermeable, moisture-vapor-permeable film bonded to the middle layer. Although the properties of the composite padding are greatly desirable, the material is difficult to use in roll form as the material untangles quite easily. Moreover, during use with an orthopedic cast, the padding tends to migrate or shift under the polyurethane-fiberglass or other immobilizing material. Thus there is a need to provide an improved padding that is easier to both apply and use, as well as prevent migration or shifting under the rigid immobilizing layer and also provides improved molding and conformance to the applied area.
As used herein, the term "porous, expanded polytetrafluoroethylene" is as disclosed in U.S. Pat. No. 3,953,566. The term "breathable" as used herein means the ability to transport moisture from the humid side of a hydrophilic member and discharge the moisture on the dry side of the member, as disclosed in U.S. Pat. No. 4,194,041. U.S. Pat. Nos. 3,953,566 and 4,194,041 in addition to U.S. Pat. No. 5,102,711 are assigned to assignee herein and all are incorporated here by reference thereto. The term quilt, quilted and quilting refer to a pattern of discretely-shaped cells.
Further as used herein, the term "biocompatible" means a material that passes the following USP biological tests without causing skin irritation or sensitization: Primary Skin Irritation TA001, Intracutaneous Reactivity Test TA044-800, and Sensitization, Maximization Method (Kligman) TA006.